[Merged by Bors] - ci(update_dependencies.yml): use lake-manifest.json in working directory rather than HEAD

[bryangingechen]

This fixes an embarrassing mistake in #30095: the script currently compares lake-manifest.json in the update-dependencies-bot-use-only branch to itself rather than to the changes made in the working directory. This has caused the update workflow to fail to push changes for about a week or so.

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[github-actions]

PR summary 724a6cb9d7

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference

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Declarations diff

No declarations were harmed in the making of this PR! 🐙

You can run this locally as follows

## summary with just the declaration names:
./scripts/declarations_diff.sh <optional_commit>

## more verbose report:
./scripts/declarations_diff.sh long <optional_commit>

The doc-module for script/declarations_diff.sh contains some details about this script.

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No changes to technical debt.

You can run this locally as

./scripts/technical-debt-metrics.sh pr_summary

• The relative value is the weighted sum of the differences with weight given by the inverse of the current value of the statistic.
• The absolute value is the relative value divided by the total sum of the inverses of the current values (i.e. the weighted average of the differences).

[TwoFX]

Thanks!
bors r+

[mathlib-bors]

Pull request successfully merged into master.

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